You can use the CloudWatch console to graph metric data generated by AWS services and your applications. Now, you can zoom into a shorter time period such as one minute or five minutes while viewing the metric graph at a longer interval.

Pan 則是維持一樣的粒度，但改變開始與結束的時間：

Once zoomed, you can also pan the metric graph across your selected interval, but at a zoomed detail level.

Traditionally, in video codec development and research, two methods have been extensively used to evaluate video quality: 1) Visual subjective testing and 2) Calculation of simple metrics such as PSNR, or more recently, SSIM.

前者因為牽涉到人工，所以不 scale，而後者跟「人的觀感」還是不夠正相關：

Without doubt, manual visual inspection is operationally and economically infeasible for the throughput of our production, A/B test monitoring and encoding research experiments.

Although researchers and engineers in the field are well-aware that PSNR does not consistently reflect human perception, it remains the de facto standard for codec comparisons and codec standardization work.